Vinylacetoxysilanes have a broad variety of applications in the chemical industry. For instance, they are useful as cross-linking silicon compounds for the preparation of compositions which have a long shelf life under exclusion of moisture and are curable at room temperature on contact with moisture to produce elastomers. Such compositions are obtained by mixing diorganopolysiloxanes containing condensable terminal groups with cross-linking silicon compounds. They also play an important role as intermediates or precursors for the preparation of compounds whose distillative purification is not without problems due to thermal instability, such as, for example, vinyltris(butanone oximato)silane.
Vinylacetoxysilane compounds can be prepared by various routes. For example, these compounds may be prepared by reacting vinylchlorosilanes with acetic acid anhydride, which produces acetyl chloride as a by-product. Vinylacetoxysilanes may also be prepared by reacting vinylchlorosilanes with acetic acid, predominantly in an inert medium. The reaction of vinylalkoxysilanes with acetic acid anhydride also results in the formation of vinylacetoxysilanes, although this method does not achieve the economic efficiency of the other above mentioned synthetic routes.
The vinylacetoxysilane products obtained by means of the above described methods have the serious disadvantage that the distillates take on a yellow to dark brown color at varying rates, that is after a few days or a few weeks subsequent to packaging. Even vinylacetoxysilanes of especially high purity, obtained by repeated fractional distillation of the products, discolor as quickly as products of only technical grade purity. Since the use of discolored vinylacetoxysilanes is not acceptable because of adverse effects upon the secondary products, long-term storage of products of this type has heretofore not been possible.